Graftable 4-amino-3-sulfinyl-substituted diphenylamine stabilizers for vulcanizates

ABSTRACT

Compounds of the formula (I) wherein R 1  is C 1 -C 18 alkyl, C 5 -C 12 -cycloalkyl, phenyl, benzyl, or allyl; n is 1 or 2; if n is 1, R 2  is C 4 -C 18 alkyl, C 5 -C 12 cycloalkyl, aryl or heteroaryl, benzyl, allyl, (CH 2 ), m COOR 3 , or is (CH 2 ) m CN; if n is 2, R 2  is —S—(CH 2 ) p —S or —S—(CH 2 ) 2 —[O—(CH 2 ) 2 ] m —S R 3  is C 1 -C 18 alkyl, benzyl, allyl; m is 1 or 2; and p is a number from 2 to 12; are suitable as a stabiliser for an elastomer to prevent oxidative, thermal, dynamic, light-induced and/or ozoneinduced degradation. They are also suitable as stabilizers for elastomers to prevent contact discoloration of substrates coming into contact with elastomers.

The present invention relates to novel stabilizers of the4-amino-3-sulfinyl-diphenylamine type, to compositions comprising anelastomer susceptible to oxidative, thermal, dynamic, or light- and/orozone-induced degradation and, as stabilizer, at least one compound ofthe 4-amino-3-sulfinyl-diphenylamine type, to the use of the stabilizersto prevent discoloration of a substrate coming into contact withelastomers, and as antiozonants for elastomers to prevent oxidative,thermal, dynamic, or light- and/or ozone-induced degradation, and alsoto the corresponding processes, and to a process for grafting thestabilizing onto elastomers.

Elastomers such as rubber products (vulcanizates), like all polymers,are susceptible to oxidative, thermal, dynamic or light-induceddegradation. A particular factor causing damage to diene rubbervulcanizates is ozone. Ozone attacks the carbon-carbon double bonds, ofwhich many remain in the rubber (vulcanizate), and, via the mechanismknown as ozonolysis, causes damage which is apparent as typical surfacecracking, and failure of the rubber product. The damage is particularlyserious when the rubber product is under dynamic stress.

To prevent ozone damage, antioxidants selected from the class consistingof para-phenylenediamines [see Russel A. Mazzeo et al., “Tire TechnologyInternational” 1994, pp. 36-46; or Donald E. Miller et al., RubberWorld, 200 (5), 13-23 (1989)] are generally added to vulcanizates. Thesecompounds have very good protective action, especially under dynamicconditions, but develop a strong intrinsic colour (discolouring) and, asa result of high migration rate, these compounds give severe contactdiscoloration (staining), i.e. the dye transfers to othersubstrates/products on direct contact. This means that the stabilizersemployed in the prior art cannot be used as stabilizers for rubberproducts which are free from carbon black or are “non-black”, and theyare also unsuitable for (black) rubber products which comprise carbonblack and are intended for use in direct contact with pale-colouredproducts.

There continues to be a need for stabilizers which, although they mayhave an intrinsic colour, are unable, for example as a result ofchemical bonding to the rubber chains, to transfer the colour to otherproducts.

It has now been found that compounds of the4-amino-3-sulfinyl-diphenylamine type are particularly suitable asstabilizers for elastomers susceptible to oxidative, thermal, dynamic,or light- and/or ozone-induced degradation.

The present invention therefore provides compounds of the formula I

wherein

-   R₁ is C₁-C₁₈alkyl, C₅-C₁₂-cycloalkyl, phenyl, benzyl, or allyl;-   n is 1 or 2;-   if n is 1, R₂ is C₄-C₁₈alkyl, C₅-C₁₂-cycloalkyl, aryl or heteroaryl,    benzyl, allyl, (CH₂)_(m)COOR₃, or-   is (CH₂)_(m)CN;-   if n is 2, R₂ is —S—(CH₂)_(p)—S or —S—(CH₂)₂—[O—(CH₂)₂]_(m)—S—-   R₃ is C₁-C₁₈alkyl, benzyl, allyl;-   m is 1 or 2; and-   p is a number from 2 to 12.

Preferred compound of formula I are those wherein

-   R₁ is C₂-C₈-alkyl, cyclohexyl, phenyl, benzyl, or allyl; especially    2-propyl, —CH(CH₃)—CH₂—CH(CH₃)₂, —CH(CH₃)—CH(CH₃)₂, 2-octyl,    cyclohexyl;-   if n is 1, R₂ is C₄-C₁₈alkyl, cyclohexyl, phenyl, benzyl,    (CH₂)₂COOR₃, or is (CH₂)₂CN;-   if n is 2, R₂ is —S—(CH₂)_(p)—S— with p ranging from 2 to 6, or is    —S—(CH₂)₂—O—(CH₂)₂—S—;    especially those wherein n is 1 and R₂ is alkyl, cyclohexyl,    (CH₂)₂COOR₃ or (CH₂)₂CN, most preferred R₂ being n-octyl, t-nonyl,    n-dodecyl, t-dodecyl; and R₃ being C₁-C₁₈alkyl, especially i-octyl,    i-tridecyl, n-dodecyl, stearyl.

Alkyl having up to 18 carbon atoms is a branched or unbranched radical,such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl,tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl,1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl,1,1,3,3-tetra-methylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl,2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl,decyl, undecyl, 1-methylundecyl, dodecyl, 1,1,3,3,5,5-hexa-methylhexyl,tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl. Oneof the preferred meanings of R₂ is C₄-C₁₈alkyl, in particularC₆-C₁₂alkyl, e.g. C₈-C₁₂alkyl.

Aryl or heteroaryl are preferably phenyl, naphthyl or pyridyl,especially phenyl.

Tert-butyl stands for 1,1-dimethylethyl; longer alkyl residues denotedas tert- or t-alkyl such as t-nonyl or t-dodecyl stand for technicalisomer mixtures of tertiary alkyl groups —C(RR′R″) wherein each of R, R′and R″ is alkyl, the total carbon number being as indicated.

Residues i-octyl or i-tridecyl are technical isomer mixtures of primaryalkyl groups (commercially available e.g. from Phillips Petroleum).

Examples for compounds of the formula I are:

Compounds of the formula I may, for example, be obtained by knownmethods, for example, from the corresponding thioethers of formula II

where n, R₁ and R₂ are as defined for formula (I), by oxidation, usuallywith an organic or anorganic peroxide or peracid. Examples are H₂O₂,H₂O₂-urea adduct, t-butylhydroperoxide, cumylhydroperoxide, performicacid, peracetic acid (or a combination of H₂O₂ /acetic acid),trichloro-peracetic acid, m-Chloroperbenzoic acid. Reactions arepreferentially carried out in an organic solvent, preferably a polarsolvent such as alcohol, ether, a ketone or mixtures thereof. Examplesfor suitable solvents are ethanol, 2-propanol, (poly)ethylene glycol,(poly)-ethylene glycol ethers, acetone, methyl-ethyl-ketone,methyl-isobutyl-ketone. Temperature is usually between −5 and +80° C.,and preferentially ranges from 35 to 50° C. The amount of oxidant can besubstoichiometric, stoichimometric or an excess. An excess of theoxidant can be destroyed be an appropriate method, e.g. washing withwater or an organic or inorganic reducing agent such as sodiumpyrosulfate. Further purification of the crude sulfoxide, e.g. withflash chromatography, is optional.

Some of the compounds of the formula II are known from WO-A-02/42262;others may be obtained in analogous manner by reacting the appropriatequinone diimine and thiol. Thus educt thioethers are obtained byreacting a quinone diimine of formula III

with a thiol of the formula IVR₂—(SH)_(n)  (IV)wherein n, R₁ and R₂ are as defined for formula (I).

Reaction conditions often are similar to those described above for theoxidation step with presence of an organic solvent and temperaturesconveniently within the range −5 to about 100° C.

The invention also provides some novel thioethers of formula II′

wherein n is 1 or 2,

-   R₁ is C₁-C₁₈alkyl, C₅-C₁₂-cycloalkyl, phenyl, benzyl, or allyl; and-   R₂, if n is 1, is tert-nonyl or tert-dodecyl or (CH₂)₂COOR₃ or    (CH₂)₂CN, where R₃ is-   C₁-C₁₈alkyl, especially i-octyl, i-tridecyl, n-dodecyl, stearyl; or-   R₂, if n is 2, is —S—(CH₂)_(p)—S— with p ranging from 2 to 6; with    the proviso that the compound of the formula II′a    is excluded.

Preferred compounds of the formula II′ are those wherein

-   n is 1 or 2, especially 1,-   R₁ is 2-propyl, —CH(CH₃)—CH₂—CH(CH₃)₂, —CH(CH₃)—CH(CH₃)₂, 2-octyl or    cyclohexyl, especially 2-propyl, and-   R₂, if n is 1, is t-nonyl or t-dodecyl or (CH₂)₂COOR₃, where R₃ is    branched C₄-C₁₈alkyl, especially i-octyl, i-tridecyl; or-   R₂, if n is 2, is —S—(CH₂)_(p)—S— with p ranging from 2 to 6.

Some compounds of formula II′ of particular technical interest are thosewherein n is 1 and

-   a) R₁ is —CH(CH₃)—CH₂—CH(CH₃)₂ and R₂ is t-dodecyl;-   b) R₁ is —CH(CH₃)—CH₂—CH(CH₃)₂ and R₂ is CH₂CH₂COO-i-octyl;-   c) R₁ is —CH(CH₃)—CH₂—CH(CH₃)₂ and R₂ is t-nonyl;-   d) R₁ is 2-propyl and R₂ is t-dodecyl;-   e) R₁ is 2-propyl and R₂ is t-nonyl.

Component b) is suitable for stabilizing elastomers, in particularpale-coloured elastomers, to prevent oxidative, thermal, dynamic, orlight- and/or ozone-induced degradation.

Elastomers are to be understood as meaning macromolecular materialswhich after considerable deformation under a small load at roomtemperature rapidly regain approximately their original shape. See alsoHans-Georg Elias, “An Introduction to Polymer Science”, Section 12.“Elastomers”, pp. 388-393, 1997, VCH Verlagsgesellschaft mbH, Weinheim,Germany or “Ullmann's Encyclopedia of Industrial Chemistry, fifth,completely revised edition, Volume A 23”, pp. 221-440 (1993).

Examples of elastomers which may be present in the compositions of theinvention are the following materials:

-   1. Polymers of diolefins, for example polybutadiene or polyisoprene.-   2. Copolymers of mono- and diolefins with one another or with other    vinyl monomers, e.g. propylene-isobutylene copolymers,    propylene-butadiene copolymers, isobutylene-isoprene copolymers,    ethylene-alkyl acrylate copolymers, ethylene-alkyl methacrylate    copolymers, ethylene-vinyl acetate copolymers,    acrylonitrile-butadiene copolymers, and also terpolymers of ethylene    with propylene and with a diene, such as hexadiene,    dicyclopentadiene or ethylidenenorbomene.-   3. Copolymers of styrene or α-methylstyrene with dienes or with    acrylic derivatives, e.g. styrene-butadiene, styrene-butadiene-alkyl    acrylate and styrene-butadiene-alkyl methacrylate; block copolymers    of styrene, e.g. styrene-butadiene-styrene, styrene-isoprene-styrene    and styrene-ethylenebutylene-styrene, and also adhesives prepared    from the latter three.-   4. Halogen-containing polymers, e.g. polychloroprene, chlorinated    rubber, chlorinated or brominated copolymer of isobutylene-isoprene    (halobutyl rubber).-   5. Natural rubber.-   6. Aqueous emulsions of natural or synthetic rubbers, e.g. natural    rubber latex or latices of carboxylated styrene-butadiene    copolymers.

The elastomers to be protected are preferably vulcanized elastomers. Ofparticular interest are natural rubber and synthetic rubber, andvulcanizates prepared therefrom. Particular preference is given topolydiene vulcanizates, halogen-containing polydiene vulcanizates,polydiene copolymer vulcanizates, in particular styrene-butadienecopolymer vulcanizates, and ethylene-propylene terpolymer vulcanizates.

Component b) is usefully added to the elastomer to be stabilized inamounts of from 0.05 to 10%, for example from 0.1 to 5%, preferably from0.5 to 3.0%, based on the weight of the elastomer to be stabilized.

In addition to components a) and b), the compositions of the inventionmay comprise other additives, such as the following:

1. Antioxidants

1.1. Alkylated monophenols, for example2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-di-methylphenol,2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol,2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol,2-(α-methylcyclohexyl)-4,6-dimethylphenol,2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol,2,6-di-tert-butyl-4-methoxymethylphenol, nonylphenols which are linearor branched in the side chains, for example 2,6-di-nonyl-4-methylphenol,2,4-dimethyl-6-(1′-methylundec-1′-yl)phenol,2,4-dimethyl-6-(1′-methylheptadec-1′-yl)phenol,2,4-dimethyl-6-(1′-methyltridec-1′-yl)phenol and mixtures thereof.

1.2. Alkylthiomethylphenols, for example2,4-dioctylthiomethyl-6-tert-butylphenol,2,4-dioctylthiomethyl-6-methylphenol,2,4-dioctylthiomethyl-6-ethylphenol,2,6-di-dodecylthiomethyl-4-nonylphenol.

1.3. Hydroquinones and alkylated hydroquinones, for example2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butylhydroquinone,2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4-octadecyloxyphenol,2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4-hydroxyanisole,3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenylstearate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate.

1.4. Tocopherols, for example α-tocopherol, β-tocopherol, γ-tocopherol,δ-tocopherol and mixtures thereof (vitamin E).

1.5. Hydroxylated thiodiphenyl ethers, for example2,2′-thiobis(6-tert-butyl-4-methylphenol), 2,2′-thiobis(4-octylphenol),4,4′-thiobis(6-tert-butyl-3-methylphenol),4,4′-thiobis(6-tert-butyl-2-methylphenol),4,4′-thiobis(3,6-di-sec-amylphenol),4,4′-bis(2,6-dimethyl-4-hydroxyphenyl)-disulfide.

1.6. Alkylidenebisphenols, for example2,2′-methylenebis(6-tert-butyl-4-methylphenol),2,2′-methylenebis(6-tert-butyl-4-ethylphenol),2,2′-methylenebis[4-methyl-6-(α-methylcyclohexyl)-phenol],2,2′-methylenebis(4-methyl-6-cyclohexylphenol),2,2′-methylenebis(6-nonyl-4-methylphenol),2,2′-methylenebis(4,6-di-tert-butylphenol),2,2′-ethylidenebis(4,6-di-tert-butyl-phenol),2,2′-ethylidenebis(6-tert-butyl-4-isobutylphenol),2,2′-methylenebis[6-(α-methylbenzyl)-4-nonylphenol],2,2′-methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol],4,4′-methylenebis(2,6-di-tert-butylphenol),4,4′-methylenebis(6-tert-butyl-2-methylphenol),1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol,1,1,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane,1,1-bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane,ethylene glycol bis[3,3-bis(3′-tert-butyl-4′-hydroxyphenyl)butyrate],bis(3-tert-butyl-4-hydroxy-5-methyl-phenyl)dicyclopentadiene,bis[2-(3′-tert-butyl-2′-hydroxy-5′-methylbenzyl)-6-tert-butyl-4-methylphenyl]terephthalate,1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butane,2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane,2,2-bis-(5-tert-butyl-4-hydroxy2-methylphenyl)-4-n-dodecylmercaptobutane,1,1,5,5-tetra(5-tert-butyl-4-hydroxy-2-methylphenyl)pentane.

1.7. O—, N— and S-benzyl compounds, for example3,5,3′,5′-tetra-tert-butyl-4,4′-dihydroxydibenzyl ether,octadecyl-4-hydroxy-3,5-dimethylbenzylmercaptoacetate,tridecyl-4-hydroxy-3,5-di-tert-butylbenzylmercaptoacetate,tris(3,5-di-tert-butyl-4-hydroxybenzyl)amine,bis(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)dithioterephthalate,bis(3,5-di-tert-butyl-4-hydroxy-benzyl)sulfide,isooctyl-3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate.

-   1.8. Hydroxybenzylated malonates, for example    dioctadecyl-2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)malonate,    di-octadecyl-2-(3-tert-butyl-4-hydroxy-5-methylbenzyl)malonate,    di-dodecylmercaptoethyl-2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate,    bis[4-(1,1,3,3-te-tramethylbutyl)phenyl]-2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonate.-   1.9. Aromatic hydroxybenzyl compounds, for example    1,3,5-tris(3,5-di-tert-butyl-4-hydroxy-benzyl)-2,4,6-trimethylbenzene,    1,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)-2,3,5,6-tetrame-thylbenzene,    2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol.-   1.10. Triazine comnounds, for example    2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4-hydroxy-anilino)-1,3,5-triazine,    2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyanilino)-1,3,5-triazine,    2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,3,5-triazine,    2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenoxy)-1,2,3-triazine,    1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate,    1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate,    2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenylethyl)-1,3,5-triazine,    1,3,5-tris(3,5-di-tert-butyl-4-hydroxy-phenylpropionyl)-hexahydro-1,3,5-triazine,    1,3,5-tris(3,5-dicyclohexyl-4-hydroxybenzyl)isocyanurate.

1.11. Benzylphosphonates, for exampledimethyl-2,5-di-tert-butyl-4-hydroxybenzylphosphonate,diethyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate,dioctadecyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate,dioctadecyl-5-tert-butyl-4-hydroxy-3-methylbenzylphosphonate, thecalcium salt of the monoethyl ester of3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid.

1.12. Acylaminophenols, for example 4-hydroxylauranilide,4-hydroxystearanilide, octylN-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate.

1.13. Esters of β-(3.5-di-tert-butyl-4-hydroxyphenyl)Prorionic acid withmono- or polyhydric alcohols, e.g. with methanol, ethanol, n-octanol,i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.

1.14. Esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)pronionic acidwith mono- or poly-hydric alcohols, e.g. with methanol, ethanol,n-octanol, i-octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol,ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethyleneglycol, diethylene glycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis-(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane;3,9-bis[2-{3-(3-tertbutyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]-undecane.

1.15. Esters of β-(3.5-dicyclohexyl-4-hydroxyphenyl)propionic acid withmono- or polyhydric alcohols, e.g. with methanol, ethanol, octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.

1.16. Esters of 3.5-di-tert-butyl-4-hydroxyphenyl acetic acid with mono-or polyhydric alcohols, e.g. with methanol, ethanol, octanol,octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol,1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethyleneglycol, triethylene glycol, pentaerythritol,tris(hydroxyethyl)isocyanurate, N,N′-bis(hydroxyethyl)oxamide,3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol,trimethylolpropane,4-hydroxymethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane.

1.17. Amides of β-(3,5-di-tert-butyl-4-hvdroxyphenyl)propionic acid e.g.N,N′-bis(3,5-di-tertbutyl-4-hydroxyphenylpropionyl)hexamethylenediamide,N,N′-bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionyl)trimethylenediamide,N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazide,N,N′-bis[2-(3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionyloxy)ethyl]oxamide(Naugard®XL-1, supplied by Uniroyal).

1.18. Ascorbic acid (vitamin C)

1.19. Aminic antioxidants, for exampleN,N′-di-isopropyl-p-phenylenediamine,N,N′-di-sec-butyl-p-phenylenediamine,N,N′-bis(1,4-dimethylpentyl)-p-phenylenediamine,N,N′-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine,N,N′-bis(1-methylheptyl)-p-phenylenediamine,N,N′-dicyclohexyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine,N,N′-bis(2-naphthyl)-p-phenylenediamine,N-isopropyl-N′-phenyl-p-phenylenediamine,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine,N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine,N-cyclohexyl-N′-phenyl-p-phenylenediamine,4-(p-toluenesulfamoyl)diphenylamine,N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine,N-allyldiphenylamine, 4-isopropoxydiphenyl-amine,N-phenyl-1-naphthylamine, N-(4-tert-octylphenyl)-1-naphthylamine,N-phenyl-2-naphthylamine, octylated diphenylamine, for examplep,p′-di-tert-octyidiphenylamine, 4-n-butyl-aminophenol,4-butyrylaminophenol, 4-nonanoylaminophenol, 4-dodecanoylaminophenol,4-octadecanoylaminophenol, bis(4-methoxyphenyl)amine,2,6-di-tert-butyl-4-dimethylamino-methylphenol,2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,N,N,N′,N′-tetramethyl-4,4′-diaminodiphenylmethane,1,2-bis[(2-methylphenyl)amino]ethane, 1,2-bis-(phenylamino)propane,(o-tolyl)biguanide, bis[4-(1′,3′-dimethylbutyl)phenyl]amine,tert-octylated N-phenyl-1-naphthylamine, a mixture of mono- anddialkylated tert-butyl/tert-octyidiphe-nylamines, a mixture of mono- anddialkylated nonyldiphenylamines, a mixture of mono- and dialkylateddodecyldiphenylamines, a mixture of mono- and dialkylatedisopropyl/isohexyl-diphenylamines, a mixture of mono- and dialkylatedtert-butyldiphenylamines, 2,3-dihydro-3,3-dimethyl-4H-1,4-benzothiazine,phenothiazine, a mixture of mono- and dialkylatedtert-butyl/tert-octylphenothiazines, a mixture of mono- and dialkylatedtert-octylphenothiazines, N-allylphenothiazine,N,N,N′,N′-tetraphenyl-1,4-diaminobut-2-ene,N,N-bis(2,2,6,6-tetramethyl-piperid-4-yl-hexamethylenediamine,bis(2,2,6,6-tetramethylpiperid-4-yl)sebacate,2,2,6,6-tetramethylpiperidin-4-one, 2,2,6,6-tetramethylpiperidin-4-ol.

2. UV absorbers and light stabilisers

2.1. 2-(2′-Hydroxtyphenyl)benzotriazoles, for example2-(2′-hydroxy-5′-methylphenyl)benzo-triazole,2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)benzotriazole,2-(5′-tert-butyl-2′-hydroxypheyl)benzotriazole,2-(2′-hydroxy-5′-(1,1,3,3-tetramethylbutyl)phenyl)benzotriazole,2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)-5-chlorobenzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-methylphenyl)-5-chlorobenzotriazole,2-(3′-sec-butyl-5′-tert-butyl-2′-hydroxyphenyl)benzotriazole,2-(2′-hydroxy-4′-octyloxyphenyl)benzotriazole,2-(3′,5′-di-tert-amyl-2′-hydroxyphenyl)benzotriazole,2-(3′,5′-bis(α,α-dimethylbenzyl)-2′-hydroxyphenyl)benzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-(2-octyloxycarbonylethyl)phenyl)-5-chlorobenzotriazole,2-(3′-tert-butyl-5′-[2-(2-ethylhexyloxy)carbonylethyl]-2′-hydroxyphenyl)-5-chlorobenzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-(2-methoxycarbonylethyl)phenyl)-5-chlorobenzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-(2-methoxycarbonylethyl)phenyl)benzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-(2-octyloxycarbonylethyl)phenyl)benzotriazole,2-(3′-tert-butyl-5′-[2-(2-ethylhexyloxy)carbonylethyl]-2′-hydroxy-phenyl)benzotriazole,2-(3′-dodecyl-2′-hydroxy-5′-methylphenyl)benzotriazole,2-(3′-tert-butyl-2′-hydroxy-5′-(2-isooctyloxycarbonylethyl)phenylbenzotriazole,2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-benzotriazole-2-ylphenol];the transesterification product of2-[3′-tert-butyl-5′-(2-methoxycarbonylethyl)-2′-hydroxyphenyl]-2H-benzotriazolewith polyethylene glycol 300;

where R=3′-tert-butyl-4′-hydroxy-5′-2H-benzotriazol-2-ylphenyl,2-[2′-hydroxy-3′-(α,α-dimethylbenzyl)-5′-(1,1,3,3-tetramethylbutyl)phenyl]-benzotriazole;2-[2′-hydroxy-3′-(1,1,3,3-tetramethylbutyl)-5′-(α,α-dimethylbenzyl)phenyl]benzotriazole.

2.2. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-methoxy,4-octyloxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2′,4′-trihydroxyand 2′-hydroxy-4,4′-dimethoxy derivatives.

2.3. Esters of substituted and unsubstituted benzoic acids, for example4-tert-butylphenyl salicylate, phenyl salicylate, octylphenylsalicylate, dibenzoyl resorcinol, bis(4-tert-butylbenzoyl)resorcinol,benzoyl resorcinol, 2,4-di-tert-butylphenyl3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl3,5-di-tert-butyl-4-hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl3,5-di-tert-butyl-4-hydroxybenzoate.

2.4. Acrylates, for example ethyl α-cyano-β,β,-diphenylacrylate,isooctyl α-cyano-β,β-diphenylacrylate, methyl a-carbomethoxycinnamate,methyl α-cyano-β-methyl-p-methoxycinnamate, butylα-cyano-β-methyl-p-methoxycinnamate, methylα-carbomethoxy-p-methoxycinnamate andN-(β-carbomethoxy-β-cyanovinyl)-2-methylindoline.

2.5. Nickel compounds, for example nickel complexes of2,2′-thiobis[4-(1,1,3,3-tetramethyl-butyl)phenol], such as the 1:1 or1:2 complex, with or without additional ligands such as n-butylamine,triethanolamine or N-cyclohexyldiethanolamine, nickeldibutyidithiocarbamate, nickel salts of the monoalkyl esters, e.g. themethyl or ethyl ester, of 4-hydroxy-3,5-di-tertbutylbenzylphosphonicacid, nickel complexes of ketoximes, e.g. of2-hydroxy-4-methylphenylundecylketoxime, nickel complexes of1-phenyl-4-lauroyl-5-hydroxypyrazole, with or without additionalligands.

2.6. Sterically hindered amines, for examplebis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(2,2,6,6-tetramethyl-4-piperidyl)succinate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonate, the condensate of1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid, linear or cyclic condensates ofN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and4-tert-octylamino-2,6-di-chloro-1,3,5-triazine,tris(2,2,6,6-tetramethyl-4-piperidyl)nitrilotriacetate,tetrakis(2,2,6,6-tetra-methyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate,1,1′-(1,2-ethanediyl)-bis(3,3,5,5-tetrame-thylpiperazinone),4-benzoyl-2,2,6,6-tetramethylpiperidine,4-stearyloxy-2,2,6,6-tetramethyl-piperidine,bis(1,2,2,6,6-pentamethylpiperidyl)-2-n-butyl-2-(2-hydroxy-3,5-di-tert-butylbenzyl)-malonate,3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione,bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate,bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)succinate, linear or cycliccondensates ofN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylene-diamine and4-morpholino-2,6-dichloro-1,3,5-triazine, the condensate of2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazineand 1,2-bis(3-aminopropylamino)-ethane, the condensate of2-chloro-4,6-di-(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazineand 1,2-bis(3-aminopropylamino)ethane,8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione,3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidine-2,5-dione,3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione,5-(2-ethylhexanoyl)-oxymethyl-3,3,5-trimethyl-2-morpholinone,1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine,1,3,5-tris(N-cyclohexyl-N-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)amino)-s-triazine,1,3,5-tris(N-cyclohexyl-N-(1,2,2,6,6-pentamethylpiperazin-3-on-4-yl)amino)-s-triazine,the reaction product of2,4-bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazinewith N,N′-bis(3-aminopropyl)ethylenediamine), a mixture of4-hexadecyloxy- and 4-stearyloxy-2,2,6,6-tetramethylpiperidine, acondensate ofN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and4-cyclohexylamino-2,6-dichloro-1,3,5-triazine, a condensate of1,2-bis(3-aminopropylamino)ethane and 2,4,6-tri-chloro-1,3,5-triazine aswell as 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No.[136504-96-6]); a condensate of 1,6-hexanediamine and2,4,6-trichloro-1,3,5-triazine as well as N,N-dibutylamine and4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No. [192268-64-7]);N-(2,2,6,6-tetramethyl-4-piperidyl)-n-dodecylsuccinimide;N-(1,2,2,6,6-pentamethyl-4-piperidyl)-n-dodecylsuccinimide;2-undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro-[4,5]decane;5-(2-ethylhexanoyl)oxymethyl-3,3,5-trimethyl-2-morpholinone; a reactionproduct of7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa-3,8-diaza-4-oxospiro-[4,5]decaneand epichlorohydrin,1,1-bis(1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyl)-2-(4-methoxyphenyl)-ethene,N,N′-bis-formyl-N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine,a diester of 4-methoxymethylenemalonic acid with1,2,2,6,6-pentamethyl-4-hydroxypiperidine,poly[methylpropyl-3-oxy-4-(2,2,6,6-tetramethyl-4-piperidyl)]siloxane, areaction product of maleic acid anhydride-α-olefin copolymer with2,2,6,6-tetramethyl-4-aminopiperidine or1,2,2,6,6-pentamethyl-4-aminopiperidine.

2.7. Oxamides, for example 4,4′-dioctyloxyoxanilide,2,2′-diethoxyoxanilide, 2,2′-dioctyloxy-5,5′-di-tert-butoxanilide,2,2′-didodecyloxy-5,5′-di-tert-butoxanilide, 2-ethoxy-2′-ethyloxanilide,N,N′-bis(3-dimethylaminopropyl)oxamide,2-ethoxy-5-tert-butyl-2′-ethoxanilide and its mixture with2-ethoxy-2′-ethyl-5,4′-di-tert-butoxanilide, mixtures of o- andp-methoxy-disubstituted oxanilides and mixtures of o- andp-ethoxy-disubstituted oxanilides.

2.8. 2-(2-Hydroxyphenyl)-1,3,5-triazines, for example2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine,2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2,4-bis(2-hydroxy-4-propyl-oxyphenyl)-6-(2,4-dimethylphenyl)-1,3,5-triazine,2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4-methylphenyl)-1,3,5-triazine,2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2-(2-hydroxy-4-tridecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2-[2-hydroxy-4-(2-hydroxy-3-butyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine,2-[2-hydroxy-4-(2-hydroxy-3-octyloxypropyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1,3,5-triazine,2-[4-(dodecyloxy/tridecyloxy-2-hydroxypropoxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2-[2-hydroxy-4-(2-hydroxy-3-dodecyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl-phenyl)-1,3,5-triazine,2-(2-hydroxy-4-hexyloxy)phenyl-4,6-diphenyl-1,3,5-triazine,2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine,2,4,6-tris[2-hydroxy-4-(3-butoxy-2-hydroxypropoxy)phenyl]-1,3,5-triazine,2-(2-hydroxyphenyl)-4-(4-methoxyphenyl)-6-phenyl-1,3,5-triazine,2-{2-hydroxy-4-[3-(2-ethylhexyl-1-oxy)-2-hydroxypropyloxy]phenyl}-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine.

3. Metal deactivators, for example N,N′-diphenyloxamide,N-salicylal-N′-salicyloyl hydrazine, N,N′-bis(salicyloyl)hydrazine,N,N′-bis(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)hydrazine,3-salicyloylamino-1,2,4-triazole, bis(benzylidene)oxalyl dihydrazide,oxanilide, isophthaloyl dihydrazide, sebacoyl bisphenylhydrazide,N,N′-diacetyladipoyl dihydrazide, N,N′-bis(salicyloyl)oxalyldihydrazide, N,N′-bis(salicyloyl)thiopropionyl dihydrazide.

4. Phosrhites and phosrhonites, for example triphenyl phosphite,diphenylalkyl phosphites, phenyldialkyl phosphites, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite,distearylpentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,bis(2,4-di-cumylphenyl)pentaerythritol diphosphite,bis(2,6-dT-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,diisodecyloxypentaerythritol diphosphite,bis(2,4-di-tert-butyl-6-methylphenyl)-pentaerythritol diphosphite,bis(2,4,6-tris(tert-butylphenyl)pentaerythritol diphosphite, tristearylsorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)4,4′-biphenylene diphosphonite,6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1,3,2-dioxaphosphocin,bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite,bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite,6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenz[d,g]-1,3,2-dioxaphosphocin,2,2′,2″-nitrilo-[triethyltris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite],2-ethylhexyl(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite,5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane.

The following phosphites are especially preferred:

Tris(2,4-di-tert-butylphenyl) phosphite (Irgafos®168, Ciba-Geigy),tris(nonylphenyl) phosphite,

5. Hydroxylamines, for example N,N-dibenzylhydroxylamine,N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine,N,N-dilaurylhydroxylamine, N,N-ditetradecylhydroxylamine,N,N-dihexadecylhydroxylamine, N, N-dioctadecylhydroxylamine,N-hexadecyl-N-octadecylhydrox-ylamine,N-heptadecyl-N-octadecylhydroxylamine, N,N-dialkylhydroxylamine derivedfrom hydrogenated tallow amine.

6. Nitrones, for example N-benzyl-alpha-phenylnitrone,N-ethyl-alpha-methyinitrone, N-octyl-alpha-heptyinitrone,N-lauryl-alpha-undecylnitrone, N-tetradecyl-alpha-tridecyinitrone,N-hexadecyl-alpha-pentadecyinitrone,N-octadecyl-alpha-heptadecyinitrone,N-hexadecyl-al-pha-heptadecyinitrone,N-ocatadecyl-alpha-pentadecyinitrone,N-heptadecyl-alpha-hepta-decylnitrone,N-octadecyl-alpha-hexadecyinitrone, nitrone derived fromN,N-dialkylhydroxyl-amine derived from hydrogenated tallow amine.

7. Thiosynergists, for example dilauryl thiodipropionate or distearylthiodipropionate.

8. Peroxide scavengers, for example esters of β-thiodipropionic acid,for example the lauryl, stearyl, myristyl or tridecyl esters,mercaptobenzimidazole or the zinc salt of 2-mercapto-benzimidazole, zincdibutyldithiocarbamate, dioctadecyl disulfide, pentaerythritoltetrakis(β-dodecylmercapto)propionate.

9. Polyamide stabilisers, for example copper salts in combination withiodides and/or phosphorus compounds and salts of divalent manganese.

10. Basic co-stabilisers, for example melamine, polyvinylpyrrolidone,dicyandiamide, triallyl cyanurate, urea derivatives, hydrazinederivatives, amines, polyamides, polyurethanes, alkali metal salts andalkaline earth metal salts of higher fatty acids, for example calciumstearate, zinc stearate, magnesium behenate, magnesium stearate, sodiumricinoleate and potassium palmitate, antimony pyrocatecholate or zincpyrocatecholate.

11. Nucleating agents, for example inorganic substances, such as talcum,metal oxides, such as titanium dioxide or magnesium oxide, phosphates,carbonates or sulfates of, preferably, alkaline earth metals; organiccompounds, such as mono- or polycarboxylic acids and the salts thereof,e.g. 4-tert-butylbenzoic acid, adipic acid, diphenylacetic acid, sodiumsuccinate or sodium benzoate; polymeric compounds, such as ioniccopolymers (ionomers). Especially preferred are1,3:2,4-bis(3′,4′-dimethylbenzylidene)sorbitol,1,3:2,4-di(paramethyl-dibenzylidene)sorbitol, and1,3:2,4-di(benzylidene)sorbitol.

12. Fillers and reinforcing agents, for example calcium carbonate,silicates, glass fibres, glass beads, asbestos, talc, kaolin, mica,barium sulfate, metal oxides and hydroxides, carbon black, graphite,wood flour and flours or fibers of other natural products, syntheticfibers.

13. Other additives, for example plasticisers, lubricants, emulsifiers,pigments, rheology additives, catalysts, flow-control agents, opticalbrighteners, flameproofing agents, antistatic agents and blowing agents.

14. Benzofuranones and indolinones, for example those disclosed in U.S.Pat. No. 4,325,863; U.S. Pat. No. 4,338,244; U.S. Pat. No. 5,175,312;U.S. Pat. No. 5,216,052; U.S. Pat. No. 5,252,643; DE-A-4316611;DE-A-4316622; DE-A-4316876; EP-A-0589839 or EP-A-0591102 or3-[4-(2-acetoxyethoxy)-phenyl]-5,7-di-tert-butyl-benzofuran-2-one,5,7-di-tert-butyl-3-[4-(2-stearoyloxyethoxy)phenyl]benzofuran-2-one,3,3′-bis[5,7-di-tert-butyl-3-(4-[2-hydroxyethoxy]phenyl)benzofuran-2-one],5,7-di-tert-butyl-3-(4-ethoxyphenyl)benzofuran-2-one,3-(4-acetoxy-3,5-dimethylphenyl)-5,7-di-tert-butyl-benzofuran-2-one,3-(3,5-dimethyl-4-pivaloyloxyphenyl)-5,7-di-tert-butyl-benzofuran-2-one,3-(3,4-dimethylphenyl)-5,7-di-tert-butyl-benzofuran-2-one,3-(2,3-dimethylphenyl)-5,7-di-tert-butyl-benzofuran-2-one.

Preferred compositions of the invention comprise, as other additives,one or more components selected from the group consisting of pigments,dyes, fillers, levelling assistants, dispersants, plasticizers,vulcanization activators, vulcanization accelerators, vulcanizers,charge control agents, adhesion promoters, light stabilizers orantioxidants, such as phenolic antioxidants (items 1.1 to 1.18 in thelist) or aminic antioxidants (item 1.19 in the list), organic phosphitesor phosphonites (item 4 in the list) and/or thiosynergists (item 7 inthe list).

An example of the concentrations at which these other additives areadded is from 0.01 to 10%, based on the total weight of the elastomer tobe stabilized.

Component b), and also, if desired, other additives are incorporatedinto the elastomer by known methods, for example during mixing ininternal mixers with rams (Banbury), on mixing rolls or in mixingextruders, prior to or during shaping or vulcanization, or else byapplying dissolved or dispersed component b) to the elastomer, ifdesired with subsequent removal of the solvent by evaporation. Whenadded to the elastomer to be stabilized, component b) and, if desired,other additives may also be in the form of a masterbatch comprisingthese, for example at a concentration of from 2.5 to 25% by weight.

Component b) and, if desired, other additives may also be added prior toor during the polymerization of synthetic elastomers or prior tocrosslinking, i.e. advantageously, if desired, as a first-levelstabilizer in the crude rubber, which may also comprise othercomponents, such as carbon black as filler and/or extender oils.

The compounds of the formula I are bonded chemically (grafted) topolymer chains under processing conditions (compounding, mixing,vulcanization, etc.). The compounds of the formula I are resistant toextraction, i.e. they continue to offer good protection after thesubstrate is subjected to intensive extraction. The loss of compounds ofthe formula I from the elastomer via migration or extraction isextremely slight. The subject of the invention therefore comprises amethod of grafting a compound of formula I onto a polymer, whichcomprises heating, preferably in a processing apparatus for polymers, amixture of polymer and at least one compound of formula I above thesoftening point of the polymer and allowing them to react with oneanother. Preferred temperature range for grafting is 120-200° C., forexample 140-180° C., especially 150-170° C.

The elastomers stabilized with the compounds of the formula I also showmarkedly improved and desirable gloss. This means that the surface glossof the elastomer stabilized according to the invention, after exposureto ozone, is significantly higher than that of an unstabilized elastomeror of an elastomer stabilized in accordance with the prior art. Asfurther advantage, the use of present compounds of formula I bringsabout significantly lowered or non-existent contact discoloration(staining).

Component b) and, if desired, other additives may be in pure form orencapsulated in waxes, in oils or in polymers when they are incorporatedinto the elastomer to be stabilized.

Component b) and, if desired, other additives may also be sprayed ontothe elastomer to be stabilized. They are capable of diluting otheradditives (e.g. the conventional additives given above) or melts ofthese, and they may therefore also be sprayed together with theseadditives onto the elastomer to be stabilized.

The resultant stabilized elastomers may be used in a wide variety offorms, e.g. ribbons, moulding compositions, profiles, conveyor belts ortyres (pneumatic).

The present invention further provides a process for stabilizingelastomers to prevent oxidative, thermal, dynamic, light-induced and/orozone-induced degradation, which comprises incorporating into these orapplying to these at least one component b).

The present invention further provides a process for preventing contactdiscoloration of substrates coming into contact with elastomers, whichcomprises incorporating into the elastomers, or applying to these, atleast one component b).

A further embodiment of the present invention is the use of component b)as stabilizers for elastomers to prevent oxidative, thermal, dynamic,light-induced and/or ozone-induced degradation.

A further embodiment of the present invention is the use of component b)as stabilizers for elastomers to prevent contact discoloration ofsubstrates coming into contact with elastomers.

The preferred compounds of the formula I [component b)] for theprocesses and uses listed above are the same as those for thecompositions of the invention.

The examples below further illustrate the invention. Data in parts orpercentages are based on weight. Room temperature stands for atemperature in the range 20-25° C. MS(Cl) denotes mass spectrometry(chemical ionization).

EXAMPLE 1 Preparation of the Compound of the Formula 1 B

The starting thioether of the formula 1A is prepared according toWO-A-02/42262, Example 3. 4.7 g (0.01 mol) of this thioether 1A and 2 g(0.018 mol) of urea-H₂O₂-adduct (30% H₂O₂) in 8 ml of ethanol arestirred for 6 hours at 40° C. After removal of the excess of hydrogenperoxide by washing of the organic phase with a solution ofsodiumpyrosulfate (Na₂S₂O₅), the solvent is removed by distillation. Thetitle sulfoxide 1B is obtained as a brown resin (yield 100%). MS(Cl) 485(MH⁺).

EXAMPLE 2 Preparation of the Compound of the Formula 2B Via Compound ofthe Formula 2A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-(1,3-dimethylbutyl)-N′-phenyl-p-quinone diimine in 25 ml ofethanol is treated at 20° C. with 3.0 mmol of tert-dodecylmercaptan withstirring. The intermediate 2A is isolated in analogy to Example 3 ofWO-A-02/42262 to give a brown oil, yield 59%, MS(Cl) 469(MH⁺).Subsequent oxidation and workup as described above in Example 1 yieldsthe title sulfoxide 2B (74% of theory) as a brown oil, MS(Cl): 485(MH⁺).

EXAMPLE 3 Preparation of the Compound of the Formula 3B Via Compound ofthe Formula 3A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-(1,3-dimethylbutyl)-N′-phenyl-p-quinone diimine is reactedwith the equimolar amount of the mercaptan HS—CH₂CH₂COO-i-octyl. Theintermediate 3A is isolated in analogy to Example 3 of WO-A-02/42262 togive a brown oil, yield 31%, MS(EI) 484(M⁺′). Subsequent oxidation andworkup as described above in Example 1 yields the title sulfoxide 3B(95% of theory) as a brown oil, MS(CI): 501 (MH⁺).

EXAMPLE 4 Preparation of the Compound of the Formula 4B Via Compound ofthe Formula 4A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-(1,3-dimethylbutyl)-N′-phenyl-p-quinone diimine is reactedwith the equimolar amount of tert-nonylmercaptan. The intermediate 4A isisolated in analogy to Example 3 of WO-A-02/42262 to give a brown oil,yield 39%, MS(EI) 426(M⁺). Subsequent oxidation and workup as describedabove in Example 1 yields the title product 4B (10% of theory) as abrown oil, MS(Cl):443(MH⁺).

EXAMPLE 5 Preparation of the Compound of the Formula 5B Via Compound ofthe Formula 5A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N′-(1,3-dimethylbutyl)-N′-phenyl-p-quinone diimine is reactedwith the equimolar amount of benzyl-mercaptan. The Intermediate 5A isisolated in analogy to Example 3 of WO-AO2/42262 to give a brown,viscous oil, yield 51%, MS(EI) 390(M⁺). Subsequent oxidation and workupas described in above Example 1 yields the title product 5B (61% oftheory) as a greenish powder, m.p. 60° C., MS(Cl) 407(MH⁺).

EXAMPLE 6 Preparation of the Compound of the Formula 6B Via Compound ofthe Formula 6A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-iso-propyl-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of n-dodecanethiol. The intermediate 6A is isolated inanalogy to Example 3 of WO-A-02/42262 to give a brownish oil, yield 75%,MS(Cl) 427(MH⁺). Subsequent oxidation and workup as described above inExample 1 yields the title product 6B (80% of theory) as colorlesscrystals, m.p. 89° C., MS(Cl) 443(MH⁺).

EXAMPLE 7 Preparation of the Compound of the Formula 7B Via Compound ofthe Formula 7A

Following the method described in Examples 1-5 of WO-A-02/42262, 3.0mmol of N-isopropyl -N′-phenyl-p-quinone diimine is reacted with theequimolar amount of n-dodecane-thiol. The intermediate 7A is isolated inanalogy to Example 3 of WO-A-02/42262 to give a brown oil, yield 89%,MS(EI) 442(M⁺). Subsequent oxidation and workup as described above inExample 1 yields the title product 7B (95% of theory) as a brown oil,MS(Cl) 459(MH⁺).

EXAMPLE 8 Preparation of the Compound of the Formula 8B Via Compound ofthe Formula 8A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-cyclo-hexyl-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of n-dodecanethiol. The intermediate 8A is isolated inanalogy to Example 3 of WO-A-02/42262 to give a brown oil, yield 56%,MS(EI) 466(M⁺). Subsequent oxidation and workup as described above inExample 1 yields the title product 8B (84% of theory) as a colorlesscrystals, m.p. 112° C., MS(Cl) 483(MH⁺).

EXAMPLE 9 Preparation of the Compound of the Formula 9B Via Compound ofthe Formula 9A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-cyclo-hexyl-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of the mercaptan HS—CH₂CH₂COO-i-octyl. The intermediate9A is isolated in analogy to Example 3 of WO-A-02/42262 to give a brownoil, yield 54%, MS(EI) 482(M⁺). Subsequent oxidation and workup asdescribed above in Example 1 yields the title product 9B (100% oftheory) as a brown oil, MS(EI) 498(M⁺).

EXAMPLE 10 Preparation of the Compound of the Formula 10B via compound10A

Following the method described in Examples 1- 15 of WO-A-02/42262, 3.0mmol of N-(2-octyl)-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of n-dodecane-thiol. The intermediate 10A is isolatedin analogy to Example 3 of WO-A-02/42262 to give a brown oil, yield 72%,MS(EI) 496(M⁺). Subsequent oxidation and workup as described above inExample 1 yields the title product 10B (100% of theory) as a brown oil,MS(Cl) 513(MH⁺).

EXAMPLE 11 Preparation of the Compound of the Formula 11B Via Compound11A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-(2-octyl)-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of t-dodecane-thiol. The intermediate 11A is isolatedin analogy to Example 3 of WO-A-02/42262 to give a brown oil, yield 57%,MS(EI): 496(M⁺). Subsequent oxidation and workup as described above inExample 1 yields the title product 11 B (24% of theory) as a brown oil,MS(Cl) 513(MH⁺).

EXAMPLE 12 Preparation of the Compound of the Formula 12B Via Compound12A

Following the method described in Examples 1-15 of WO-A-02/42262, 3.0mmol of N-(2-octyl)-N′-phenyl-p-quinone diimine is reacted with theequimolar amount of the mercaptan HS—CH₂CH₂COO-i-octyl. The intermediate12A is isolated in analogy to Example 3 of WO-A-02/42262 to give a brownoil, yield 54%, MS(Cl) 513(MH⁺). Subsequent oxidation and workup asdescribed above in Example 1 yields the title product 12B (100% oftheory) as a brown oil, MS(Cl) 529(MH⁺).

EXAMPLE 13 Stabilization of Black Vulcanizate

40.0 parts by weight of Cariflex® 1220 [polybutadiene, SHELL] areprocessed on mixing rolls at 60° C. with 60.0 parts by weight of naturalrubber and 55.0 parts by weight of carbon black (N 330), 6.0 parts byweight of Ingralen 450 (RTM) [extender oil], 5.0 parts by weight of zincoxide [vulcanization activator], 2.0 parts by weight of stearic acid[vulcanization activator], 0.2 parts by weight of IRGANOX 1520 (RTM)[processing stabilizer, Ciba Specialty Chemicals], 2.0 parts by weightof sulfur [vulcanizer], 0.6 part by weight of Vulkacit MOZ (RTM)[vulcanization accelerator, BAYER] and 1.5 parts by weight of thestabilizer to be tested according to Tables 1, 2 and 3, to give ahomogeneous mixture, the vulcanization system [sulfur and Vulkacit MOZ(RTM)] not being added until the end of the mixing process. The mixtureis vulcanized in electrical heating presses at 150° C. to T95 on therheometer curves, to give elastomer sheets of 2 mm thickness, 21 cmlength and 8.0 cm width. Sections of the 2 mm rubber sheets are placedon a white cardboard underlay and stored in a circulating-air cabinet at50° C. for 5 days. The contact surface or its margin is then evaluatedvisually for contact discoloration (staining): 0 =no discoloration (orthe discoloration of the reference in which no AO is present) and 5=greatest degree of discoloration. The results are summarized inTable 1. TABLE 1 Example Stabilizer Staining (4 weeks) 13a^(b))  1B 013b^(b))  2B 0 13c^(b))  3B 0 13d^(b))  4B 0 13e^(b))  6B 0 13f^(b))  8B0 13g^(b)) 10B 0 13h^(b)) 11B 0 13i^(a)) Vulkanox 4020^(c)) 5 13k^(a))Vulkanox 4010^(d)) >3 13l^(a)) UOP688^(e)) >2 13m^(a)) Flexzone6H^(f)) >4 ^(a))Comparative example. ^(b))Example according to theinvention. ^(c))Vulkanox 4020 (RTM) [Bayer] is 4-(1,3-dimethylbutyl)aminodiphenylamine of the formula A.

(A) ^(d))Vulkanox 4010 (RTM([Bayer] is 4-(2-propylamino)diphenylamine offormula B.

(B) ^(e))UOP 688 (RTM) [UOP] is 4-(2-octylamino)diphenylamine of formulaC.

(C) ^(f))Flexzone 6H (RTM) [Flexsys] is 4-cyclohexlyaminodiphenylamineof formula D

(D)

Determination of the grafting rate: In order to test the extractionresistance of the compounds according to the invention, the 2mm plateswere treated in a Soxhiet extractor for 72 hours in acetone. Thenon-extractable portion of additive was determined by nitrogen analysiswith allowance for extractable and extraction-stable nitrogen from othercomponents of the mixture. The results are summarized in Table 2. TABLE2 Non-extractable Example Stabilizer additive^(g)) [%] 13a^(a)) 1A 013b^(b)) 1B 5 13c^(a)) 2A 0 13d^(b)) 2B 47 13e^(a)) 3A 0 13f^(b)) 3B 3213g^(a)) 4A 0 13h^(b)) 4B 48 13i^(a)) 6A 0 13j^(b)) 6B 18 13k^(a)) 8A 013l^(b)) 8B 11 13m^(b)) 11B 48 13n^(a)) Vulkanox 4020^(c)) 0^(a))Comparative example.^(b))Example according to the invention.^(c))see footnote at end of Table 1.^(g))by nitrogene analysis, after Soxhlet extraction with acetone (72h).

Oxidation protection of extracted samples: To ascertain the effect ofthe grafted additives hot air ageing in a multi-cell oven (DIN 53508)was carried out with extracted specimens. The anti-oxidative effect ofthe additives was determined by tensile tests with ISO S2 dumb-bells(DIN 53504). The higher the tensile strength the better the protection.The results are summarized in Table 3. TABLE 3 Tensile strength [MPa] ofextracted samples after Example Stabilizer 2 weeks oven aging at 80° C.13a^(a)) 1A 4.9 13b^(b)) 1B 6.4 13c^(a)) 2A 6.2 13d^(b)) 2B 8.3 13e^(a))3A 5.3 13f^(b)) 3B 8.9 13g^(a)) 4A 6.1 13h^(b)) 4B 10.8 13i^(b)) 5B 6.613j^(a)) 8A 5.4 13k^(b)) 8B 7.9 13l^(a)) Vulkanox 4020^(c)) 5.3Explanations of footnotes ^(a)),^(b)) and ^(c)) see end of Table 1.

1. A compound of the formula I

wherein R₁ is C₁-C₁₈alkyl, C₅-C₁₂-cycloalkyl, phenyl, benzyl, or allyl; n is 1 or 2; if n is 1, R₂ is C₄-C₁₈alkyl, C₅-C₁₂-cycloalkyl, aryl or heteroaryl, benzyl, allyl, (CH₂)_(m)COOR₃, or is (CH₂)_(m)CN; if n is 2, R₂ is —S—(CH₂)_(p)—S or —S—(CH₂)₂—[O—(CH₂)₂]_(m)—S— R₃ is C₁-C₁₈alkyl, benzyl, allyl; m is 1 or 2; and p is a number from 2 to
 12. 2. Compound of formula I according to claim 1 wherein R₁ is C₂-C₈-alkyl, cyclohexyl, phenyl, benzyl, or allyl, if n is 1, R₂ is C₄-C₁₈alkyl, cyclohexyl, benzyl, phenyl, (CH₂)₂COOR₃, or is (CH₂)₂CN; if n is 2, R₂ is —S—(CH₂)_(p)—S or —S—(CH₂)₂—[O—(CH₂)₂]_(m)—S—; R₃ is C₁-C₁₈alkyl; and p is a number from 2 to
 6. 3. A composition comprising a) a naturally occurring or synthetic elastomer susceptible to oxidative, thermal, dynamic, light-induced and/or ozone-induced degradation, and b) as stabilizer, at least one compound of the formula I according to claim
 1. 4. A composition according to claim 3, in which component a) is a natural or synthetic rubber or a vulcanizate prepared therefrom.
 5. A composition according to claim 4, in which component a) is a polydiene vulcanizate, a halogen-containing polydiene vulcanizate, a polydiene copolymer vulcanizate or an ethylene-propylene terpolymer vulcanizate.
 6. A composition according to claim 3, further comprising one or more components selected from the group consisting of pigments, dyes, fillers, levelling assistants, dispersants, plasticizers, vulcanization activators, vulcanization accelerators, vulcanizers, charge control agents, adhesion promoters, antioxidants, flame retardants, UV absorbers and light stabilizers, phenolic antioxidants, aminic antioxidants, organic phosphites or phosphonites and thiosynergists.
 7. A thioether of formula II′

wherein n is 1 or 2, R₁ is C₁-C₁₈alkyl, C₅-C₁₂-cycloalkyl, phenyl, benzyl, or allyl; and R₂, if n is 1, is tert-nonyl or tert-dodecyl or (CH₂)₂COOR₃ or (CH₂)₂CN, where R₃ is C₁-C₁₈alkyl, R₂, if n is 2, is —S—(CH₂)_(p)—S— with p ranging from 2 to 6; with the proviso that the compound of the formula II′a

is excluded.
 8. A method of grafting a compound of formula I according to claim 1 onto an elastomer, which method comprises heating a mixture of elastomer and at least one compound of formula I above the softening point of the elastomer and allowing them to react with one another.
 9. (canceled)
 10. A process for stabilizing an elastomer to prevent oxidative, thermal, dynamic, light-induced and/or ozone-induced degradation and preventing contact discoloration of substrates coming into contact with the elastomer, which process comprises incorporating into these or applying to these at least one compound of formula I according to claim
 1. 11. A composition comprising according to claim 3 where the at least one compound of the formula I is present in an amount from 0.05 to 10%, based on the weight of component a).
 12. A thioether of formula II′ according to claim 7 where R₂, if n is 1, is tert-nonyl or tert-dodecyl or (CH₂)₂COOR₃ or (CH₂)₂CN, where R₃ is i-octyl, i-tridecyl, n-dodecyl or stearyl. 